Capacitance type seat occupant sensor system

Abstract

A capacitance type seat occupant sensor system of a vehicle includes an AC electric power source, a main electrode disposed at a seat of the vehicle to form an electric field between the main electrode and the body of the vehicle, a guard electrode disposed between a seat frame and the main electrode, a switch unit for establishing connection of the guard electrode to have the same potential as the main electrode to provide a seat occupant sensing mode, an impedance calculating unit for calculating an impedance of a sensing circuit based on the AC voltage and an amount of current flowing through the sensing circuit, a real-part-and-imaginary-part calculating unit and judging unit for discriminating an occupant on the seat based on at least the imaginary part of the first impedance. The impedance calculating unit calculates a first impedance of an electric circuit including the main electrode when the switch means provides the seat occupant sensing mode, and the real-part-and-imaginary-part calculating unit calculates the real part and the imaginary part of the impedance.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application is based on and claims priority from Japanese Patent Application 2006-296529, filed Oct. 31, 2006, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a capacitance type seat occupant sensor system to be installed in a vehicle.[0004]2. Description of the Related Art[0005]JP-Hei-11-271463-A discloses a seat occupant sensor system that includes a capacitance type sensor and an electronic control system. The capacitance type sensor includes a main electrode disposed inside a seat of a vehicle to detect a change in an electric field that is formed between the main electrode and a portion of a vehicle body.[0006]If no occupant sits on the seat, there is nothing but air in the electric field. If there is a member of a child restraint system (CRS) on the seat, the member intervenes in the electric field. If a passenger s...

AI Technical Summary

Benefits of technology

[0013]An object of the invention is to provide a capacitance type occupant sensor system that can discriminate an occupant of a seat with high accuracy.

[0014]Another object of the invention is to provide a capacitance type occupant sensor system that can detect malfunction of the system and wet seat.

Problems solved by technology

Because the dielectric constant of the water is 80 and close to the dielectric constant of the human body, it is difficult to discriminate the human body without additional sensor if the seat is wetted by water.

Therefore, it is difficult to discriminate an occupant on the seat with high accuracy.

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